1. Field of the Invention
This invention relates to an herbal drug composition for the prevention and treatment of senile dementia.
2. Description of the Related Art
Recently, many research studies have focused on Alzheimer's disease (AD), a senile dementia, in the biochemical, genetic and medical aspects. Dementia may refer to a general decline in all areas of cognitive function and intellectual ability which may significantly impair one's professional job, usual social activities or personal relations. More specifically, its main symptoms include a cognitive function impairment and various mental disorders in language, judgment and perceptive vasospastic ability as well as serious difficulty in acquisition of new technologies. Personality changes and emotional restlessness soon become apparent and ultimately lead to death. Dementia, which adversely affects the intrinsic activity of cerebrum, is a peculiar symptom associated with the fundamental disorders of brain induced by various factors. Due to loss of cerebral parenchyma, the brain was grossly shrunken in size and occasionally, a frontal lobe and temporal lobe are more severely shrunken, being accompanied by the expansion of ventricle in most cases. A large number of cerebral cortex cells, Purkinje cells in the cerebellum, or cells of the spinal cord shrink in size. The cause of Alzheimer's disease is unknown but it has been reported that from the autopsy of brain in dead patients with Alzheimer's disease, the level of neurotransmitter acetylcholine (ACh) was significantly reduced. Some drugs, which are still under research, aim to improve the cognitive function for the treatment of dementia and to alleviate the secondary mental disorders of dementia such as anxiety, delusion, irritation, insomnia and abnormal behavior. Some of the commercially available anti-dementia agents include COGNEX and ARICEPT, which were approved by Food and Drug Administration of U.S.A. These drugs inhibit the activity of acetylcholine esterase (AChE) acting mainly on the central nervous system, thus increasing the level of neurotransmitter acetylcholine for the prevention and treatment of dementia. Results of clinical studies using some drugs to inhibit the AChE activity indicate that improved memory enhancement was attained at synaptic clefts in the brain.
However, a majority of the conventional anti-dementia agents may produce serious cholinergic effects in the peripheral nerve with an extremely short half-life and serious side effects such as hepatotoxicity (ref: Br. J. Psychiatry, 138, 46, 1981). Further, Cognex (9-amino-1,2,3,4-tetrahydroacridine, THA), which has been widely used for the treatment of dementia, is effective in significant enhancement of cognitive ability in AD patients during oral administration (ref: N, Engl. J. Med., 315, 1241, 1986) but much adverse reactions such as tremor, dizziness and cytotoxicity have still encountered.